App Validation Issue - Bot must send a proactive welcome message in personal scope

Thank you for the clarification.

Now I understand that for app validation, I need to keep the personal chat welcome message in on_members_added_activity and implement deduplication based on conversation ID. My planned approach is to create a database table that stores the tenant ID and conversation ID when a welcome message is sent, then remove the entry on app uninstall. This should prevent duplicate welcome messages triggered by the Graph API queries. I'll test this implementation and report back on the results.

I still have some confusion about point 2 regarding reading chat history using conversation references. From my testing, the conversation reference and chat ID appear to be different for one-to-one chats. Could you point me to sample code or detailed documentation on this topic? (Ideally showing how to use conversation references to get chat history). 

Thank you for your support.